The technology of the present disclosure relates to a fixing device including a fixing roller, a pressure roller brought into press contact with the fixing roller, and an electricity removing unit for removing charge of a surface of the pressure roller, and an image forming apparatus including the fixing device.
In an electrophotographic image forming apparatus, a thermal roller type fixing device, in which a fixing roller having a heater therein and a pressure roller are brought into press contact with each other such that a paper carrying an unfixed toner image passes through between these rollers so that toner is fixed to the paper, has been widely used.
In such a fixing device, each of the fixing roller and the pressure roller has a release layer of a fluororesin and the like on the surface thereof. Therefore, due to frictional electrification between these two rollers at the time of rotational driving of the fixing roller and the pressure roller, charge transfer when a paper subjected to transfer passes through a fixing nip, and the like, the surface of each roller is easy to be charged, so that the surface of the pressure roller may be charged to minus several thousands of voltages. As a consequence, when a charging polarity of unfixed toner on a paper is negative, there is a problem that the unfixed toner moves to the surface of the fixing roller by repulsive force from the surface of the pressure roller. Furthermore, when the charging polarity of the unfixed toner is positive, negative charge leaks at the fixing nip, so that electrostatic attractive force of the unfixed toner for a paper is reduced and thus the unfixed toner moves to the surface of the fixing roller. When the toner having moved to the surface of the fixing roller is attached to the paper again, the image quality of a fixed image is degraded.
In this regard, a technology, in which a conductive brush including a plurality of conductive fiber bristles is arranged in the vicinity of the pressure roller and discharge occurs between a front end of each conductive fiber bristle and the surface of the pressure roller so that negative charge on the surface of the pressure roller is removed, has been proposed. Between the front end of each conductive fiber bristle and the surface of the pressure roller, a space is provided to cause the discharge.